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Low oil pressure/No start

02mountain

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fort worth, tx
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02 Mountaineer
My Moutaineer just would not start one day after work. It turns over but it will not fire up. It shows low oil pressure with the guage not reading at all. I had it towed home and used a code reader and it would not pull any codes. My first guess would be the oil pressure sender but could it be something else? Any help would be appreciated.
 



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I doubt it's low oil pressure because if you turn the key on and wait a sec, mine will say the same. Have someone turn the ignition on and you need to have your ear over the gas cap, when the ignition is turned on you should hear a "hmmm." Don't try to start it;) If you hear a "hmmm" that mean the fuel pump is working, if not, then it may be a fuse or be bad. It's worth a shot?

Just hard to say because it could be a number of things. How was it running before this happened? Did it ever act funny in any way?

Do you have a 4.0 v6 or 4.6 v8?
 






I haven't tried the fuel pump yet so hopefully that is all it is.

There were no problems leading up to this so I don't know.

It is a 4.6 V8.
 






Your oil pressure won't read anything until the motor fires...there is no oil pressure unless it's running.

I just had the same issue with my explorer, had a bad fuel pump as well as a faulty coolant temp sensor...neither threw up a CEL or codes, took 2 shops to diagnose the issue, had the dealer do the work.

Could be anything from a faulty idle air control assembly, an ignition issue (coil pack, wires/plugs), or a sensor issue (MAF, coolant temp, oil pressure, fuel pressure). The ECU utilizes 4 sensors when you fire off your truck, to push the correct amount of fuel/air into the motor for it to fire. In my case, my coolant temp sensor was faulty, and my truck thought my coolant temp was at normal running temperature, on a cold unfired motor. This equated into it not pumping enough fuel for the air mixture into the motor (lean), because the coolant temp sensor was telling the ECU it was a 'warm' motor, causing it to not fire. When the coolant temp sensor was replaced, all was fine....

But my fuel pump was also replaced at the same time, because it was on the fritz, and was offering 0 PSI too often and I had the dealer replace it as well as the fuel filter.

So it may sound quirky, but unless the 4 sensors are all working properly, your truck won't fire on a cold motor...your computer won't give it the correct fuel/air mixture it needs to fire.

If you can afford it, take it to the dealer and have them run a 'driving diagnostic' on it...this is what they had to do for me, since mine wasn't throwing any codes and no CEL was on. Ended up being the damn coolant temp sensor...
 






I haven't tried the fuel pump yet so hopefully that is all it is.

I just want to add...you don't want to "hope that's all it is", the fuel pump isn't a cheap part at all, and if you're planning to do the work yourself, dropping the tank isn't a blast either. An aftermarket fuel pump assembly starts at about $200 and goes up from there if you want a Ford part (~ $400 )...so not the best part to break. I would hope it's just a sensor...they are all in the $30-$40 range (except for the MAF of course)
 






If you can afford it, take it to the dealer and have them run a 'driving diagnostic' on it...this is what they had to do for me, since mine wasn't throwing any codes and no CEL was on. Ended up being the damn coolant temp sensor...

What is a driving diagnostic and around how much would it cost?
 






I had a problem with my oil pump lately. Seems when i turn the truck on, the low oil pressure warning comes on and the needle bottoms out. It would stay like this for like 2 minutes or so and go back to normal. My guess was the temperature got cold enough that the oil got thick enough that it made it hard to pump thru until the oil heated up some. That was in about 30F degrees and below temp. It has been about mid 40's when I start my truck up lately and doesnt do it anymore.
 












What is a driving diagnostic and around how much would it cost?

Ford charged me $95 for that diagnostic, it's what they charge when they can't hit you up for $60-$65 for a normal diagnostic which is pretty much nothing more than pulling codes....but if theres no codes and no CEL showing, then they have to do the 'driving diagnostic' which basically means a tech really looks through your entire system by hand, and determines what the issue is (you know...how shops used to do things).
 






:mad:I would suggest you dont get to use to the needle bottoming out. My 92 started that right after having the heads rebuilt. Went from the tic, tic, of rockers to bam, bam, of main bearings. Seems that the oil pump was failing and now I have a filter and pan full of metal. cant wait to get it apart.
 






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